Exhaust system and a method of producing the same

ABSTRACT

An exhaust system for use in combination with a combustion engine. The exhaust system includes a silencer having an outer casing that defines an interior and an internal construction within the interior and co-extruded with the outer casing so that the outer casing and the internal construction constitute a one-piece extrusion. The outer casing has a length in a longitudinal direction and a substantially uniform cross-section in a transverse direction. The internal construction has at least one wall that extends the length of the outer casing to define with the outer casing at least two longitudinal chambers within the interior of the outer casing. The wall has a deformed portion and passages through the deformed portion so that the silencer has a path through which gas flows from a first of the two longitudinal chambers and through the passages into the second longitudinal chamber, resulting in noise reduction for the combustion engine.

The present invention relates to an exhaust system to be used incombination with a combustion engine comprising an exhaust pipe and asilencer.

Such an exhaust system is generally known.

Automotives of the types, which are powered by combustion engines, areequipped with an exhaust system in order to lower the noise emitted fromthe engine. The known exhaust system consists of one or more large potsor chambers acting as silencers, which are interconnected by pipes. Theyare normally placed underneath the automotive, where they take up aconsiderable amount of space. In modern design, where the use of spaceis optimised in order to maximise the exploitation of the availablespace, a less space consuming solution is heavily sought. Also, the sizeand shape of the known exhaust systems have a negative influence on theaerodynamic properties of the automotive. This is another importantaspect, since the aerodynamic properties must be optimised in order tominimise fuel consumption, and thereby also pollution. A furthernegative aspect of the known exhaust systems is, that the weight isgenerally high due to the use of steel in the design. Steel has verypoor resistance against corrosion at high temperatures, which leads toincreased wall thickness of the pots and pipes, in order to prolong thelife span (until corrosion has penetrated the wall thickness). Theincreased wall thickness leads to increased weight, which also leads toincreased fuel consumption. To slow down corrosion, an aluminium coatingis often applied to steel exhaust systems, which do at least partlywork, but makes it difficult to recycle the used exhaust systems,because of the mixing of the basic materials. Also, exhaust systems madefrom stainless steel have been proposed, but these are expensive due tothe high price of the material, and difficult to produce as stainlesssteel is harder to machine and to braze than standard steel.

One objective of the present invention is to provide an exhaust systemwith improved aerodynamic properties. Another objective is to provide anexhaust system, which is less space consuming. A further objective is toprovide an exhaust system with reduced weight. A further objective is toprovide an exhaust system with improved life span.

According to the invention these objects are obtained in that theexhaust system consists of an outer casing of a mainly uniformcross-section and an internal system comprising a number of chambers andpassages, acting as noise reduction for the combustion engine.

An exhaust system with outer casing of mainly uniform cross-section doesnot have the shifts in dimensions and numerous sharp edges as the knowntypes of systems, whereby the aerodynamical properties are greatlyenhanced. The outer casing of mainly uniform cross-section and theinternal system comprising a number of chambers and passages allow adesign of the exhaust system, which consumes less space and with reducedweight. The exhaust system may be made from a light metal such asaluminium, whereby the life span may be increased to any chosen time,and at the same time reducing the overall weight.

The invention further relates to a method for producing an exhaustsystem as described above.

The method of producing the exhaust system comprises extruding at leastan outer casing, and providing a system of internal walls so as to formchambers and passages acting as noise reduction for the combustionengine.

It is hereby obtained, that the exhaust system may be produced at a lowcost, since an even complex design of the cross-section of the casing ispossible with insignificant effect on the cost. This is to some degreedue to the use of the extrusion process to produce it.

The method may comprise extrusion of at least part of the chambers,whereby this may be made with the same advantages as the outer casing.

The method may comprise plastic deformation to form at least part of thechambers, in order to provide these with suitable designs for optimisingthe reduction of the noise emitted.

The method may comprise forming of passages, whereby accurate and/orsmall as well as large passages may be formed of any shape or form.

The method may comprise insertion of blockings in order to provide morefreedom of design.

The method may comprise foaming an inlet and/or an outlet, whereby thesemay be integrated in the design. Alternatively, these may be attachedsubsequently, e.g. by welding.

In the following the invention is described with reference to thedrawings, which display examples of embodiments of the invention;

FIG. 1 shows an embodiment of a cross-section of a profile for anexhaust system

FIG. 2 shows another embodiment of a cross-section of a profile for anexhaust system

FIG. 3 shows a further embodiment of a cross-section of a profile for anexhaust system

FIG. 4 shows another embodiment of a cross-section of a profile for anexhaust system

FIG. 5 shows section A-A of the profile according to FIG. 4

FIG. 6 shows an end view of an exhaust system

FIG. 7 shows section B-B according to FIG. 6

FIG. 8 shows section EBB according to FIG. 6, with arrows indicating theflow of gas through the exhaust system

FIG. 9 shows a cross-section of another profile for an exhaust system

FIG. 10 shows a schematic view of an exhaust system using the profileaccording to FIG. 9

FIG. 11 shows a finished exhaust system as it can be fitted to a car.

FIG. 1 displays an outer casing 2 comprising a first profile withanother profile placed inside, which other profile comprises a number ofwalls 3. The outer casing 2 is shaped to have good aerodynamicproperties. The walls 3 of the inner profile are suitable forconstituting internal divisions inside an exhaust system after furtherprocessing.

FIGS. 2, 3 and 4 display different designs of an outer casing 2, whichis extruded as one piece including internal walls 3.

FIG. 5 displays section A-A of FIG. 4 with an outer casing 2 andinternal walls 3.

FIG. 6 displays an exhaust system comprising the profile of FIGS. 4 and5. The exhaust system comprises an outer casing 2 with internal walls 3.At one side the wall 3′ is plastically deformed and passages 6 have beenmachined, e.g. punched, drilled etc. At the other side, the casing 2′and internal wall 3″ are plastically deformed to form an inlet 14. Alsopassages 6 have been formed as well as chambers 4, which are more clearin FIG. 7.

FIG. 7 essentially displays section B-B of FIG. 6. However, blockings orbaffles 12 have been added to close the ends and to further separate thechambers 4. The outer casing 2 and the walls 3 have been deformed at theends to form an inlet 14 and an outlet 16. Further chambers 4 have beenformed, e.g. by using mandrels. In suitable places, passages 6 have beenformed to allow flow of gas between the chambers 4. The passages 6 maybe of any size, shape and form. The sizes, shapes and forms of thechambers 4 as well as the passages 6 are design parameters, which arecalculated using known technical formulas corresponding to the flow ofgas, speed, desired noise reduction etc., which is knowledge of theskilled person.

FIG. 8 is in essence identical to FIG. 7. Only arrows indicating theflow of gas through the inlet 14 via a chamber 4 through passages 6 intothe next chamber 4 etc. have been added.

According to the invention, the design of the exhaust system can assumea variety of shapes, sizes and forms depending on the kind ofautomotive, its use, the kind of engine etc.

If convenient, the inlets 14 and outlet 16 may be equipped with pipesfor easy connection to other components. Especially the outlet 16 may beequipped with a piece of pipe designed to accommodate a specific soundof the engine. The inlet 14 may be connected directly to a combustionchamber, to a manifold or e.g. to a catalytic unit and/or a smallparticle filter.

FIG. 9 shows another tube 20 to be used as basic profile for an exhaustsystem according to the invention. The exact cross-section of thisprofile is not critical, as long as it is adapted to be mounted to theunderside of a car. In view thereof it has a flat part 21 and curvedparts 22, 23. At the junctions between the curved parts 22, 23 asemicircular part 24 has been provided, extending over substantiallymore than 180° C., so that a tube with circular cross-section andsuitable diameter can be fixed into this part 24.

In order to make an exhaust system as shown in FIG. 10, baffles 25having a cross-section corresponding to the cross-section of the tube 20of FIG. 9, except for the circular part 24 which is left open, areinserted through one end and positioned at defined distances from thatend. This can be done in a way corresponding to the way in which bafflesare positioned in manifolds such as disclosed e.g. in EP-A-0 891 528 orEP-A-0 214 670. In this way the tube 20 is divided into a number ofspaces divided by the baffles and interconnected through thesemicircular parts 24. These volumes of these spaces can be adapted tothe requirements of the exhaust system to act as a silencer.

An improvement can be made by inserting circular tube ends 26 into thesemicircular parts 24 and position these tube ends 26 in such a way thateither one end is in the same plane as a baffle or each of the tube endsextend into one of two neighbouring spaces divided by a baffle 25. Inthis way the silencing can be optimized.

Baffles 25 and tube ends 26 can be fixed inside the tube 20 by weldingprocess commonly used in the art.

In FIG. 11 there is shown the final shape of an exhaust system as can bemade according to the invention, and which can be applied directly tothe bottom part of a car. Because of the larger cross-section of thetube the exhaust line has sufficient strength and at the same timesufficient volume for noise reduction. In view of this latterrequirement bending of the extruded profile is important to havesufficient length and thereby sufficient volume for noise reduction andto fit to the bottom of a car. This bending may also be important inview of other structural elements fitted to the bottom of the car, suchas driving axle etc.

The silencer may be made using steel/steel alloys, but is preferablymade using light metal alloys, such as titanium, aluminium, magnesium.It may also comprise components made from ceramic materials. Plastics,with or without reinforcements may also be used in part or as a whole.Optionally with an internal shield for improved heat resistance.

1. Exhaust system to be used in combination with a combustion engine,the exhaust system comprising a silencer comprising an outer casingdefining an interior and an internal construction within the interiorand co-extruded with the outer casing so that the outer casing and theinternal construction constitute a one-piece extrusion, the outer casinghaving a length in a longitudinal direction and a substantially uniformcross-section in a transverse direction, the internal constructioncomprising at least one wall that extends the length of the outer casingto define with the outer casing at least two longitudinal chamberswithin the interior of the outer casing the at least one wall having adeformed portion and passages through the deformed portion so that thesilencer comprises a path through which gas flows from a first of the atleast two longitudinal chambers and through the passages into a secondof the at least two longitudinal chambers resulting in noise reductionfor the combustion engine.
 2. Exhaust system according to claim 1,further comprising at least one baffle separating one of the at leasttwo longitudinal chambers into two longitudinally-aligned chambers. 3.Exhaust system according to claim 1, wherein the outer casing is amultiport extruded tube-element.
 4. Exhaust system according to claim 1,wherein the deformed portion is transverse to the longitudinal directionand contacts the outer casing.
 5. Exhaust system according to claim 1,wherein the outer casing and the internal construction consistessentially of aluminium or an aluminium alloy.
 6. Exhaust systemaccording to claim 1, wherein the outer casing and the at least one wallhave complementary deformed end portions that together define an openinginto the silencer.
 7. A method of producing an exhaust system, themethod comprising: co-extruding an outer casing and an internalconstruction within an interior of the outer casing so that the outercasing and the internal construction constitute a one-piece extrusion,the outer casing being extruded to have a length in a longitudinaldirection and a substantially uniform cross-section in a transversedirection, the internal construction being extruded to comprise at leastone wall that extends the length of the outer casing to define with theouter casing at least two longitudinal chambers within the interior ofthe outer casing; and then deforming the at least one wall to define adeformed portion and forming passages through the deformed portion sothat the silencer comprises a path through which gas flows from a firstof the at least two longitudinal chambers and through the passages intoa second of the at least two longitudinal chambers, resulting in noisereduction for the combustion engine.
 8. A method according to claim 7,further comprising the step of installing at least one baffle toseparate one of the at least two longitudinal chambers into twolongitudinally-aligned chambers.
 9. A method according to claim 7,further comprising the step of shaping the outer casing to fit beneathan undercarriage of an automobile.
 10. A method according to claim 7,wherein the deformed portion is deformed so as to be oriented transverseto the longitudinal direction.
 11. A method according to claim 7,wherein the deformed portion is deformed so as to contact the outercasing.
 12. A method according to claim 7, wherein the outer casing andthe internal construction consist essentially of aluminium or analuminium alloy.
 13. A method according to claim 7, further comprisingthe step of deforming the outer casing and the at least one wall to havecomplementary deformed end portions that together define an opening intothe silencer.
 14. A method according to claim 7, wherein the deformedportion is deformed so as to separate one of the at least twolongitudinal chambers into two longitudinally-aligned chambers. 15.Exhaust system according to claim 1, wherein the deformed portionseparates one of the at least two longitudinal chambers into twolongitudinally-aligned chambers.
 16. Exhaust system to be used incombination with a combustion engine, the exhaust system comprising asilencer comprising an outer casing defining an interior and an internalconstruction within the interior and co-extruded with the outer casingso that the outer casing and the internal construction constitute aone-piece extrusion, the outer casing having a length in a longitudinaldirection and a substantially uniform cross-section in a transversedirection, the internal construction comprising at least one walldefining a semicircular opening, the silencer further comprising atleast one baffle separating the interior into at least twolongitudinally-aligned chambers and a tubular member received in thesemicircular opening and interconnecting the two longitudinally-alignedchambers so that the silencer comprises a path through which gas flowsfrom a first of the two longitudinally-aligned chambers and through thetubular member into a second of the two longitudinally-aligned chambers,resulting in noise reduction for the combustion engine.
 17. Exhaustsystem according to claim 16, wherein the outer casing and the internalconstruction consist essentially of aluminium or an aluminium alloy.